The present invention relates to locking fixation assemblies used in bone fixation.
Neurological and orthopedic surgeons performing spine surgery use fixation plates to treat spinal disorders including spinal anomalies, spinal injuries, disc problems and bone problems to effect fusion of vertebrae. These fixation plates are typically held by one or more screws passing through the plate and into the vertebrae above and below the injured or replaced disc. During installation of the fixation plate, the screws must be allowed to be positioned by the surgeon to provide best fitted conformity to enhance fusion rates. Misalignment can lead to fracture of the screws or wear-inducted loosening in the fixation plate assembly. There is thus a need for an easily installed fixation plate that accommodates variable angles between the fixation screws and the fixation plate.
Many of the current fixation plates are rigid. An unduly stiff plate can result in undue wear between the screws and plates which can in extreme cases lead to fracture of the screws or wear-induced flexibility in the fixation assembly. Further, some limited amount of flexibility conforms to the normal modulus of elasticity and allows impact forces to be more readily accommodated and thereby enhances fusion rate. There is thus a need for a fixation plate that can better handle sudden forces without damaging the fixation assembly or the vertebrae fastened to the fixation plate. The plate may or may not be attached to a separate cage implant.
Several current fixation plates are thick or have parts protruding from the plate, causing the overlying muscle and tissue to rub against the plate or protuberances, leading to irritation of the abutting tissue and irritation of the patient. There is thus a need for a fixation plate that reduces the irritation of the abutting and adjacent tissue.